Worldwide, over 2 billion people suffer from worm infections (hookworm, Ascaris and Trichuris, collectively referred to as soil-transmitted helminths (STHs)) in developing countries. STHs contribute to the overwhelming burden of poverty and deprivation in areas where adverse health, social, economic, education and other related factors predominate. STH infection in childhood results in short-term and lifelong disability, including malnutrition (e.g. underweight, stunting and wasting), cognitive impairment and increased susceptibility to other infection, among others. Mass deworming programs in school-age children are recommended by the World Health Organization (WHO). WHO also recommends deworming of preschool children (as of 12 months of age) in endemic areas; however, the benefits of deworming on improving growth and development, especially in the 12-24 month age group, have been inadequately studied. This knowledge is crucial because, with appropriate nutrition and health interventions, all children have a similar potential for healthy growth and development, provided that such interventions occur in the critical window of opportunity before the age of two.